Washington (CNN) - The lawmaker gunning for Democrats to keep control of the House this fall said that a Republican loss in a Tuesday special election shows that the GOP strategy for taking back the House has "hit a brick wall."

Democratic Congressional Campaign Committee Chairman, Rep. Chris Van Hollen, D-Maryland, spoke to a small group of reporters at the Democratic National Committee headquarters on Thursday.

Van Hollen talked about his party's win in Pennsylvania's 12th congressional district. The special election was held to fill the remaining term of the late Democratic Rep. John Murtha. Democrat Mark Critz, a former Murtha staffer, beat Republican candidate Tim Burns. He was sworn in on Thursday.

The district is considered socially conservative. And some political observers considered it a must-win for Republicans.

Van Hollen said that in the race, voters heard the Republican message, "And they rejected it."

Washington (CNN) – Democrat Mark Critz was sworn in Thursday as a member of the House of Representatives.

Critz won a special House election Tuesday to fill a vacant seat in Pennsylvania's 12th Congressional district after topping Republican Tim Burns by double digits in the battle to succeed the late Democratic Rep. Jack Murtha.

Critz was a longtime aide to Murtha, who represented the district for 18 terms until he passed away from complications following gallbladder surgery this year.

"This moment is bittersweet for me because I wouldn't be here right now if Jack Murtha hadn't left us too soon," Critz told lawmakers, after being sworn in on the floor of the House.

(CNN) – Keep your eyes on southwestern Pennsylvania. While it's being overshadowed by higher-profile Senate primaries, a special election Tuesday for a House seat that represents that part of the state has drawn national attention and could have national implications.

And while the winners in the Senate primaries move onto the general election in November, the victor in this contest goes directly to Congress.

Republican Tim Burns is battling Democrat Mark Critz to fill the seat of the late Rep. John Murtha.

The race has stepped up in intensity over the past month, with both campaigns as well as national party committees going up with television ads.

(CNN) – Two hard-hitting new ads are heating up the Pennsylvania battle for the late Rep. Jack Murtha's congressional seat.

Republican Tim Burns is facing off against Democrat Mark Critz in a the May 18 special election. The race has stepped up in intensity in recent weeks, with both campaigns as well as national party committees going up with television ads.

The Burns campaign came out Tuesday with a new television commercial that questions the ethics of Critz, a longtime aide to Murtha, a Democrat who represented the district for 18 terms until he passed away earlier this year.

"Mark Critz. A Washington bureaucrat bankrolled by Pelosi. Critz was investigated by the congressional ethics office and Critz was in charge of the finances for a company caught on paying their taxes," says the narrator in the ad.

"The Ethics Committee found that Mr. Murtha did nothing wrong. Tim Burns knows this," Critz told CNN, responding to Burns' ad. "I worked for Parkins, a local small business, because I wanted to try to help my brother-in-law's company turn around its operations so that it could bring jobs to our community. I left because I disagreed with decisions that were being made over the company's future. These misleading personal attacks are Tim Burns' attempt to distract from his own record on job loss and outsourcing."

(CNN) - Former Alaska Gov. Sarah Palin announced her support Monday for Pennsylvania Republican Tim Burns.

"I'm proud to offer my support to Tim Burns in his campaign to bring real job creation to Pennsylvania's 12th district," Palin said in a post on her Facebook page. The former GOP vice presidential hopeful also pointed to Burns' involvement in the Tea Party movement as a reason for her endorsement.

Burns will face Democrat Mark Critz in a May 18 special election for the House seat held for decades by the late Democratic Rep. John Murtha.

Vice President Joe Biden will be in Pennsylvania Friday to fundraise for two Democrats.

Washington (CNN) - Vice President Joe Biden heads to Pennsylvania Friday to lend a hand to two fellow Democrats.

Friday morning Biden headlines a fundraiser in Pittsburgh for Mark Critz, the Democratic candidate in the May 18 special election to fill the seat of the late Rep. Jack Murtha, a Democratic source tells CNN.

Critz, a longtime aide to the late congressman, is facing off against Republican Tim Burns. The race has heated up in recent weeks, with both campaigns as well as national party committees going up with television ads.

The district, which stretches from Cambria County in west-central Pennsylvania down to the southwestern corner of the state, is considered socially conservative. In the 2004 presidential election, Sen. John Kerry won the district by 2 points. Sen. John McCain narrowly edged out Barack Obama in the district in 2008, even though Obama carried the state by 10 percent.

Following the fundraiser, the vice president heads east, where he'll be the main attraction at a rally for Sen. Arlen Specter. The event, Friday afternoon at the Wilkes-Barre/Scranton International Airport, brings Biden close to his native Scranton for the first time since becoming vice president.